Flexible induction electrode



APril 21, 1959 s. K. RASMUSSEN 2,882,904

FLEXIBLE INDUCTION ELECTRODE Filed April 7, 1954 2 Sheets-Sheet 1 April21, 1959 s. K. RAsMussEN 2,882,904 FLEXIBLE INDUCTION ELECTRODE FiledApril 7. 1954 2 Sheets-Sheet 2 United States Patent C) FLEXIBLEINDUCTION ELECTRODE Sherrill K. Rasmussen, Milton Junction, Wis.,assignor to The Burdick Corporation, Milton, Wis., a corporation ofDelaware Application April 7, 1954, Serial No. 421,612

7 Claims. (Cl. 128-418) This invention relates to a therapeuticapplicator and, more particularly, to a flexible induction electrode forapplying high frequency oscillations to a desired object.

It is an object of the present invention to provide a new and improvedtherapeutic applicator.

Another object is to provide an improved flexible induction electrodefor applying high frequency oscillations.

A still further object of this invention is to provide a flexibleapplicator having an improved construction permitting the symmetricallocation of the applicator terminals.

Another object is to provide a flexible induction electrode includingnew and improved means for preventing both the displacement ofelectrical conductors from the electrode and the application ofexcessive forces to the induction element forming a portion of theelectrode assembly.

In accordance with these and many other objects, one embodiment of theinvention comprises a flexible body of insulating material forming acavity within which is mounted a flexible flat convolute inductionelement, the ends of which are spaced different distances inwardly fromthe edge of the insulating body. The body member is provided with a pairof symmetrically located and spaced hollow flexible protuberancesforming terminal assemblies through which extend conductorsinterconnecting an external power supply with the ends of the inductionelement. These terminal assemblies include elongated portions extendinggenerally along the longitudinal axis of the induction electrode topermit the conductors to be electrically connected to the ends of theinduction element without requiring the terminal assemblies to beincongrously spaced in accordance with the actual location of the endsof the induction element. The terminal assemblies also include strainrelief means for preventing the application of the excessive forces tothe flexible induction element and for preventing the externalconnectors from being displaced from the induction electrode assembly.

Many other objects and advantages of the present invention will beapparent from a consideration of the following specification when readin conjunction with the drawings wherein:

Fig. 1 is a top plan view of a flexible induction electrode embodyingthe present invention;

Fig. 2 is a front elevational view of the electrode shown in Fig. 1;

Fig. 3 is an enlarged cross sectional view taken along line 33 in Fig. 1showing the construction of a terminal;

Fig. 4'is a bottom plan view of the applicator shown in Fig. 1 with alower cover member removed;

Fig. 5 is an enlarged fragmentary cross sectional View taken along line55 in Fig. 1 showing the terminal construction; and

Fig. 6 is a perspective view showing a typical applicationof theflexible induction electrode embodying the present invention.

. Referring now to Figs. 1, 4, and 6 of the drawings, a

flexible induction electrode, indicated generally as 10, comprises abody 12 of flexible dielectric material such as molded rubber having ashallow recess 14 within which is secured, as by cement, a flexible flatconvolute body of electrically conductive material forming an inductionelectrode element 16. A cover member 18 (Figs. 3 and 5) is secured tothe body member 12 and the induction element 16 to enclose the latter.The induction element is electrically connected to an external source ofpower (not shown) by means of a pair of insulated cables 20 which extendinto the body 12 of the electrode 10 through a pair of terminalassemblies indicated generally as 22 and 24. The ends of the cables 20are provided with insulated plugs 26 which are received within jacks(not shown) on the external source of power.

The electrode 10, in being formed entirely of flexible materials,readily conforms to the configuration of the object to which the highfrequency oscillations are to be applied and thus facilitates themaximum transmission of oscillatory energy from the electrode 10 to theobject. As shown in Fig. 6, the electrode 10 may be positioned onportions of the human body and secured in position thereon by a flexiblestrap 28, both ends of which are detachably secured to the body of theelectrode 10.

Referring now to the induction element 16, this may be formed in a flatconvolute configuration by stamping a sheet of electrically conductivematerial, such as copper or a'copper alloy. The thickness of the sheetis so chosen that it is thin enough to be readily flexible but is alsothick enough to prevent buckling or permanent physical distortion of theelement 16 when this element is flexed during the application of theelectrode 10 to an object. The thickness may be about .0l0-.012 inchwhich is approximately the depth of the recess 14. Further, in additionto being electrically conductive, the material forming the element 16 ispreferably somewhat resilient so that this element will return to anormal uniplanar configuration when the electrode 10 is removed from theobject to which the high frequency energy is applied.

The convolute induction element 16 of the present invention is formed sothat a pair of ends 30 and 32 thereof lie on substantially a centrallydisposed line extending longitudinally relative to the element 16. Theend 32 is spaced inwardly from the edge of the body 12 a greaterdistance than the end 30 to permit the element 16 to be formed by asingle stamping operation on a unitary metal blank, but the terminalassemblies 22 and 24 are symmetrically located with respect to the outerconfiguration of the body member 12.

Referring now to the terminal assemblies 22 and 24, each of theseassemblies includes a hollow receptacle or sleeve 36 integrallyconnected with the body 12 by a skirt portion 38 which is enlarged orelongated in a direction generally corresponding to the longitudinalaxis of the electrode 10. The walls defining the sleeve 36 and the skirtportion 38 may be slightly thicker than those forming the body 12 inorder to provide strong securing means for the cables 20.

In order to connect the induction element 16 with the external source ofpower, a pair of hollow flexible braided conductors 40 are provided. Asshown in Fig. 4, the end 56 of one of the conductors 40 is secured tothe outer end 36 of the induction element 16, and this conductor extendsoutwardly through the terminal assembly 24 into a flexible insulatingcovering or sleeve 42 forming a part of one of the cables 20. An end 56of the other conductor 40 is secured to the inner end 32 of the element16 and extends outwardly through the terminal assembly 22 into aninsulating sleeve 42 forming a part of the other cable 20. It isdesirable to use the hollow braided type of conductor 45] shown in thedrawings rather than conventional solid electrical conductors in orderto reduce the loss of energy in transmitting the high frequencyoscillations from the external source to the induction element 16. V

.Apleasing appearance is provided by locating-terminal assemblies 22 and24 symmetrically with respect to the body 12 of the inductor 10 eventhough the ends 30 and 32 f the induction element 16, to which theconductors 40 must be connected, are not symmetrically located relativeto, the exterior configuration of the inductor 10. However, theprovision of the enlarged portions 38 extending substantially along thelongitudinal axis of the body member 12 permits the conductors 40 to beelectrically connected to the ends of the induction element 16irrespecfive of their spacing relative to the edge of the body member 12while permitting the terminal assemblies 22 and 24 through which theseconductors pass to be located in identical positions relative to theexternal-configuration "of the electrode 10.

'40 extending through the terminal assembly 24 is displaced, to theright and is connected to the outer end 30 ofthe induction element 16.Further, the end of the conductor 40 extending through the terminalassembly '22 is also displaced to the right, as shown in Fig. 4, land iselectrically connected to the inner end 32 of the induction element 16,which end 32 is displaced inwardly from the edge of the body member 12 agreater distance than is the end 30. Obviously, the induction element 16could be positioned oppositely to that shown in Fig. 4 and the enlargedportions 38 of the terminal assemblies 22 and 24 would permit a similarinterconnection of the conductors 40 with this element.

- In order to prevent the displacement of the conductors 40 from withinthe terminal assemblies 22 and 24 and also to prevent the application ofexcessive forces to the flexible induction element 16, strain reliefmeans are provided in each of these terminal assemblies. As shown inFigs. 3 and 5, the sleeve 36 is provided with an internal tapered wall44 terminating in a shoulder 46. A rigid dielectric plug 48 having atapered annular outer wall 50 is seated in the sleeve 36 so that ashoulder 52 thereon engages the shoulder 46 and so that the tapered wall50 engages the tapered wall 44. The tapered walls 44 and 50 and theinterlocked shoulders 46 and 52 positively prevent the plug 48 frombeing displaced from the sleeve .36. The tubular body of the conductor40 extends through an opening 54in the plug 48.

In order to secure the conductor 40 to the strain relief plug 48, theend 56 of the conductor 40 is flattened (after removal of the centralfilling, if one is present in the conductor) so that the width of thisflattened portion exceeds the diameter of the opening 54 and thisflattened portion is soldered, as indicated at 58, to provide a rigidprojection engaging the lower edge of the rigid plug 48. Also, a drop ofsolder or similar securing means 59 may be applied to the conductor 40above the plug 48 to prevent the conductor from being forced into theenlarged portion 38. In this manner, the force applied to the conductor40, which tends to pull this conductor out of the terminal assemblies 22and 24, is directly transmitted through the rigid plug 48 to theflexible structure forming the terminal assemblies. Accordingly, thestrain relief plug 48 not only prevents the conductor 40 from beingdisplaced from within the terminal assemblies 22 and 24 but alsoprevents this conductor from being pulled out of electrical contact withthe flexible induction element 16.

In order to provide means for both securing the insulating sleeve 42 tothe terminal assemblies 22 and 24 and for maintaining this sleeve in aspaced relation to the braided conductor 40, the rigid plug 48 isprovided with an integral sleeve portion 60. The end of the flex iblesleeve 42 is inserted between the inner wall of the sleeve 36 and theouter surface of the sleeve 60 and is resiliently held in engagementtherewith to secure the location of the terminal assemblies 22 and 24,the (Di/$1 1 4 sleeve 42 to the terminal assemblies 22 and 24 and toalso maintain the spacing between the braided conductor 40 and the innersurface of the insulating sleeve 42.

To provide a completely sealed enclosure for the flexible inductionelement 16, the body 12 of the induction electrode 10 is provided with arecessed ledge 64 (Fig. 4) and a lip 66 defining a peripheral U-shapedchannel. The cover member 18 is coated with cement and this member isthen placed on the body member 12 with the peripheral portion thereofreceived within the channel formed by the lip 66. The cement produces abond between the peripheral portion of the cover member 18 and the ledge64, and the cement on the remaining portions of the cover member 18produces a bond between this member and the outer surface of theflexible induction element 16 and body member 12, thereby positivelysecuring the element 16 in a desired position on the induction.electrode 10, as shown in Figs. 3- and 5.

.- As shown in Fig. 4 of the drawings, the conductor I Toincfeasethe-flexibility f thelinduiml ball the body member 12 and the covermember 18 are provided with a plurality of transversely extending ribs70 and 72, respectively. These ribs increase the flexibility of theelectrode 10 to permit this element to conform to the outerconfiguration of the human body, as shown in Fig, 6, but increase therigidity of the electrode 10 insofar as deflection or flexure about alongitudinal axis is concerned soas to maintain the edges of theelectrode in contact with the object. Further, the provision of theribs. provides a means for desired spacing of the in duction element 16from the object and for permitting a flow of air between the surface ofthe object and the electrode 10 thereby to reduce undesirable heatingeffects. The electrode 10 is detachably mounted on a human body by theflexible securing means 28 which is provided at each end thereof with aplurality of longitudinally spaced'apertures 76. In order detachably tosecure the flexible securing means 28 to the electrode 10, a pair offasteners 78 are provided. These fasteners extend through slots 80 and82 in the body 12 and the covering member 18 and include flangedportions 84 and 86 (Fig. 5) for maintaining the fasteners 78 withinthese slots. The upper end of the fastener 78 is tapered, as indicatedat 90, and is provided with a neck portion 92. When one of the apertures76 is placed on the tapered portion 90 and the strap 28 is presseddownwardly toward the flange 86, the material defining the opening 76 isdistorted and subsequently snaps back into engagement with the neckportion 92, thereby detachably securing the flexible strap 28 to theinduction electrode 10. As shown in Fig. l of the drawings, the flexiblestra 28'is1 secured to the induction electrode 10 at points thereonwhich are in substantial alignment with and are closely adjacent to theterminal assemblies 22 and 24. Therefore, the forces applied to the body12 of the electrode 10, due either to manipulation of the cables 20 orto the Weight thereof, are directly transmitted from the terminalassemblies 22 and 24 to the flexible securing means 28 without beingtransmitted through an appreciable length of the body member 12. Sincethese forces are directly transmitted to the supporting means throughthe relatively strong constructions forming the terminal assemblies 22and 24, excessive stresses are not applied to the relatively thinmaterial forming the flexible body 12. Accordingly, the flexibleinduction electrode 10 provides a new and improved constructionutilizing an easily and cheaply fabricated flat flexible convoluteinduction element 16 which is completely sealed within a flexible insulating body and in which the inner and outer ends there: of areadapted to be connected to an external source of power through terminalassemblies symmetrically dis posed with respect to the outerconfiguration of the electrode 10.- I-lurther, by the advantageousformation of the body member 12 and covering member 18 and by a properalL; flexibility of the induction; electrode .10. is increased therebyto permit this electrode to readily conform to the configuration of theobject to which it is applied without structurally weakening treelectrode to the extent that this electrode cannot be held in intimateengagement with this object. The provision of strain relief means in theterminal assemblies 22 and 24, which are of increased structuralstrength, not only prevents the application of excessive forces to theflexible induction element 16 and prevents the conductors 20 from beingdisplaced from the electrode 10 but also results in the transmission offorces substantially directly fromthe cables 20 to the flexiblesupporting means 28.

While the present invention has been described in connection with thedetails of a specific embodiment of the invention, it should beunderstood that these details are not to be construed as a limitation ofthe invention except insofar as set forth in the accompanying claims.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A therapeutic electrode comprising a relatively thin flexible bodyhaving a recess therein, a flexible convolute layer of electricallyconductive material mounted in said recess, said convolute layer havinga pair of terminals positioned different distances from the edge of saidbody, hollow means communicating with said recess and symmetricallymounted on said flexible body, said hollow means having enlargedportions extending longitudinally of said body and over said terminals,conductors connected to said terminals and extending through said hollowmeans, and said flexible body including means for securing said body toan object, said securing means being fastened to said body at spacedpoints in line with said terminals and including apertured strap meansand fastening means secured to said body at spaced points thereon, saidfastening means including two spaced portions of reduced diameter, afirst of said reduced diameter portions being engaged by said body andthe second of said reduced diameter portions being detachably receivedwithin one of the apertures in said strap means.

2. A therapeutic electrode comprising a generally flat backing memberformed of flexible material having a recess substantially coextensivewith said backing material and a pair of relatively rigid spaced hollowreceptacles formed therein, said spaced hollow receptacles communicatingwith said recess and extending outwardly from said backing member, aflat convolute body of flexible electrically conductive strip materialmounted in said recess, a cover member formed of flexible material andsecured to said backing member to enclose said flat body within saidelectrode, electrically conductive means connected to spaced points onsaid body and extending through said hollow receptacles, and strainrelief means mounted in said receptacles and including means engagingsaid conductive means to prevent forces applied to said conductive meansfrombeing transmitted to said flat body and to cause said forces to betransmitted to said relatively rigid receptacles.

3. A therapeutic electrode comprising a body of flexible material havinga cavity therein, a flexible flat convolute lamina of electricallyconductive material mounted in said cavity, a hollow member incommunication with said body and having an enlarged hollow flexibleportion connecting a narrow portion thereof to said body and extendingtransversely of the axis of the body, and a conductor connected to saidconvolute lamina and extending out of said cavity through said hollowmember, said con- 6 ductor having insulation secured to said hollowmember at said narrow portion thereby to prevent displacement of saidconductor from said body.

4. A therapeutic electrode comprising a flexible body defining a recess,flat convolute conducting means motmted in said recess, flexible hollowmeans mounted on said body in communication with said recess, saidhollow means having a constricted portion, rigid means defining anopening and mounted in said constricted portion, a flexible braidedhollow electrical conductor connected to said conducting means andextending through said opening, said braided conductor being flattenedat a point adjacent said rigid means, and means for maintaining saidbraided conductor in a flat configuration so that forces applied to saidconductor are transmitted to said rigid means.

5. A therapeutic electrode comprising an elongated flexible body formedof flexible material and having a recess therein, a flat convolute layerof electrically conductive material mounted in said recess, a coverformed of flexible material and secured to said body for closing saidrecess to define a cavity within which the electrically conductivematerial is received, and ribs formed in said body and said coverextending transversely thereto to permit said electrode to be flexedlaterally and to resist longitudinal flexure thereof, said ribs on saidcover also spacing said electrode from an object to which said electrodeis applied.

6. A therapeutic electrode comprising a flexible body having a shallowrecess of a predetermined depth therein, a flat stamped lamina ofelectrically conductive material mounted in said recess, the thicknessof said lamina eing approximately equal to said predetermined depth,said stamped lamina having a pair of terminals positioned differentdistances from the edge of said body, hollow means communicating withsaid recess and symmetrically mounted on said flexible body, said hollowmeans having enlarged portions extending over said terminals, andconductors connected to said terminals and extending through said hollowmeans.

7. A therapeutic electrode comprising a flexible body having a firstrecess of a predetermined depth therein, a fiat layer of electricallyconductive material mounted in said first recess, the thickness of saidlayer being approximately equal to said predetermined depth, said layerhaving a pair of terminals positioned different distances from the edgeof said body, hollow means in communication with said recess andsymmetrically mounted on said flexible body, said hollow means havingenlarged portions extending over said terminals, conductors connected tosaid terminals and extending through said hollow means, said body havinga second recess therein, means formed integral with said body andcooperating with said second recess to form a channel, and a flexibleplate received in said channel and secured to said second recess forenclosing said flat layer.

References Cited in the file of this patent UNITED STATES PATENTS1,975,518 Rose Oct. 2, 1934 2,110,392 Don Mar. 3, 1938 2,404,283Gieringer July 16, 1946 2,476,645 Wantzenberg July 19, 1949 2,509,417Bowers May 30, 1950 2,583,853 Kazdin Jan. 29, 1952 UNITED STATES PATENTOFFICE Q CERTIFICATE OF CORRECTION Patent Noo 2,882,904 April 21, 1959Sherrill Ko Rasmussen It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionand that the said Letters Patent should read as corrected below.

Column 6, line- 18, strike out ilexible", first occurrence; line 19,after "flat" insert flexible Signed and sealed this 8th day of December1959 (SEAL) Attest:

KARL Ho AXLINE Attesting Officer ROBERT C. WATSON Commissioner ofPatents

